[FFmpeg-devel] [PATCH v3] libavcodec/v4l2_buffers.c: set AVFrame interlaced flags

[Zhao Zhili]

> On Dec 19, 2024, at 20:45, Zhao Zhili <quinkblack at foxmail.com> wrote:
> 
> 
>> On Dec 19, 2024, at 08:28, James Almer <jamrial at gmail.com> wrote:
>> 
>> On 12/18/2024 6:59 PM, Scott Theisen wrote:
>>> Originally from:
>>> https://github.com/MythTV/mythtv/commit/669955c6cb29196b4b5120451b5b998d67a65749
>>> ---
>>> v3:
>>> remove unnecessary clearing of already 0 valued flags
>>> use switch-case; I don't really think it is any simpler, but I do like the format better.
>>> ---
>>> libavcodec/v4l2_buffers.c | 19 +++++++++++++++++++
>>> 1 file changed, 19 insertions(+)
>>> diff --git a/libavcodec/v4l2_buffers.c b/libavcodec/v4l2_buffers.c
>>> index 23474ee143..19cc86334b 100644
>>> --- a/libavcodec/v4l2_buffers.c
>>> +++ b/libavcodec/v4l2_buffers.c
>>> @@ -210,6 +210,24 @@ static enum AVColorTransferCharacteristic v4l2_get_color_trc(V4L2Buffer *buf)
>>>     return AVCOL_TRC_UNSPECIFIED;
>>> }
>>> +static void v4l2_get_interlacing(AVFrame *frame, V4L2Buffer *buf)
>>> +{
>>> +    enum v4l2_field field;
>>> +    field = V4L2_TYPE_IS_MULTIPLANAR(buf->buf.type) ?
>>> +        buf->context->format.fmt.pix_mp.field :
>>> +        buf->context->format.fmt.pix.field;
>>> +
>>> +    switch (field) {
>>> +    case V4L2_FIELD_INTERLACED:
>>> +    case V4L2_FIELD_INTERLACED_TB:
>>> +        frame->flags |=  AV_FRAME_FLAG_TOP_FIELD_FIRST;
>>> +        /* fallthrough */
>>> +    case V4L2_FIELD_INTERLACED_BT:
>>> +        frame->flags |=  AV_FRAME_FLAG_INTERLACED;
>>> +        break;
>>> +    }
>>> +}
>>> +
>>> static void v4l2_free_buffer(void *opaque, uint8_t *unused)
>>> {
>>>     V4L2Buffer* avbuf = opaque;
>>> @@ -434,6 +452,7 @@ int ff_v4l2_buffer_buf_to_avframe(AVFrame *frame, V4L2Buffer *avbuf)
>>>     frame->color_trc = v4l2_get_color_trc(avbuf);
>>>     frame->pts = v4l2_get_pts(avbuf);
>>>     frame->pkt_dts = AV_NOPTS_VALUE;
>>> +    v4l2_get_interlacing(frame, avbuf);
>>>       /* these values are updated also during re-init in v4l2_process_driver_event */
>>>     frame->height = avbuf->context->height;
>> 
>> Should be ok, but i don't maintain (nor can test) v4l2. So if nobody reviews it or pushes it in a few days, I'll.
> 
> I’m planing to do some test, maybe this weekend.

Applied.

Unfortunately I tried two devices, but neither of them support interlaced decoding, and rpi5 only support
stateless v4l2 which isn’t supported by FFmpeg yet.

> 
>> 
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>